The present invention relates to a circuit board that is superior in heat dissipation and that has a compact structure, and to an electronic circuit chip-mounted circuit board where electronic circuit chips are mounted on the circuit board. The invention also relates to a circuit board apparatus in which such chip-mounted circuit boards are mounted on a mother board.
Electronic circuit chips generate heat during operation. If these circuit chips are not cooled down, the temperature of the chips is increased so that the chips would not be operated normally. It is therefore necessary to cool the chips. The electronic circuit chips are generally mounted on a circuit board. There is such a technique according to the prior art that, in order to cool the electronic circuit chips mounted on the circuit board, fins are provided on electronic circuit chips or packages, and these fins are cooled by air or water. In addition, as shown in U.S. Pat. No. 4,608,407 and Japanese Patent Unexamined Publication No. 61-248500 (A), cooling plates are mounted on an outside of the circuit board to cool the electronic circuit packages. There is also proposed a system, as shown in Japanese Patent Unexamined Publication No. 62-198200 (A), in which cooling liquid is in a box-shaped heat panel in intimate contact with the circuit board in an interior or a back side of the circuit board. Also, it is proposed to provide a circuit chip-mounted circuit board with a specific guide member for defining a duct for cooling circuit chips on the circuit board (Japanese Patent Unexamined Publication No. 56-148898).
However, the above-described prior art proposals do not take into consideration the space needed for the cooling equipment and cost thereof. It has been difficult to mount plural or multiple circuit boards, on which chips are mounted, with a high density. In addition, the cost per one circuit board has been high.